crypto/cmac.c

   1 /*
   2  * CMAC: Cipher Block Mode for Authentication
   3  *
   4  * Copyright © 2013 Jussi Kivilinna <jussi.kivilinna@iki.fi>
   5  *
   6  * Based on work by:
   7  *  Copyright © 2013 Tom St Denis <tstdenis@elliptictech.com>
   8  * Based on crypto/xcbc.c:
   9  *  Copyright © 2006 USAGI/WIDE Project,
  10  *   Author: Kazunori Miyazawa <miyazawa@linux-ipv6.org>
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  */
  18
  19 #include <crypto/internal/hash.h>
  20 #include <linux/err.h>
  21 #include <linux/kernel.h>
  22 #include <linux/module.h>
  23
  24 /*
  25  * +------------------------
  26  * | <parent tfm>
  27  * +------------------------
  28  * | cmac_tfm_ctx
  29  * +------------------------
  30  * | consts (block size * 2)
  31  * +------------------------
  32  */
  33 struct cmac_tfm_ctx {
  34         struct crypto_cipher *child;
  35         u8 ctx[];
  36 };
  37
  38 /*
  39  * +------------------------
  40  * | <shash desc>
  41  * +------------------------
  42  * | cmac_desc_ctx
  43  * +------------------------
  44  * | odds (block size)
  45  * +------------------------
  46  * | prev (block size)
  47  * +------------------------
  48  */
  49 struct cmac_desc_ctx {
  50         unsigned int len;
  51         u8 ctx[];
  52 };
  53
  54 static int crypto_cmac_digest_setkey(struct crypto_shash *parent,
  55                                      const u8 *inkey, unsigned int keylen)
  56 {
  57         unsigned long alignmask = crypto_shash_alignmask(parent);
  58         struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent);
  59         unsigned int bs = crypto_shash_blocksize(parent);
  60         __be64 *consts = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
  61         u64 _const[2];
  62         int i, err = 0;
  63         u8 msb_mask, gfmask;
  64
  65         err = crypto_cipher_setkey(ctx->child, inkey, keylen);
  66         if (err)
  67                 return err;
  68
  69         /* encrypt the zero block */
  70         memset(consts, 0, bs);
  71         crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts);
  72
  73         switch (bs) {
  74         case 16:
  75                 gfmask = 0x87;
  76                 _const[0] = be64_to_cpu(consts[1]);
  77                 _const[1] = be64_to_cpu(consts[0]);
  78
  79                 /* gf(2^128) multiply zero-ciphertext with u and u^2 */
  80                 for (i = 0; i < 4; i += 2) {
  81                         msb_mask = ((s64)_const[1] >> 63) & gfmask;
  82                         _const[1] = (_const[1] << 1) | (_const[0] >> 63);
  83                         _const[0] = (_const[0] << 1) ^ msb_mask;
  84
  85                         consts[i + 0] = cpu_to_be64(_const[1]);
  86                         consts[i + 1] = cpu_to_be64(_const[0]);
  87                 }
  88
  89                 break;
  90         case 8:
  91                 gfmask = 0x1B;
  92                 _const[0] = be64_to_cpu(consts[0]);
  93
  94                 /* gf(2^64) multiply zero-ciphertext with u and u^2 */
  95                 for (i = 0; i < 2; i++) {
  96                         msb_mask = ((s64)_const[0] >> 63) & gfmask;
  97                         _const[0] = (_const[0] << 1) ^ msb_mask;
  98
  99                         consts[i] = cpu_to_be64(_const[0]);
 100                 }
 101
 102                 break;
 103         }
 104
 105         return 0;
 106 }
 107
 108 static int crypto_cmac_digest_init(struct shash_desc *pdesc)
 109 {
 110         unsigned long alignmask = crypto_shash_alignmask(pdesc->tfm);
 111         struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
 112         int bs = crypto_shash_blocksize(pdesc->tfm);
 113         u8 *prev = PTR_ALIGN((void *)ctx->ctx, alignmask + 1) + bs;
 114
 115         ctx->len = 0;
 116         memset(prev, 0, bs);
 117
 118         return 0;
 119 }
 120
 121 static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p,
 122                                      unsigned int len)
 123 {
 124         struct crypto_shash *parent = pdesc->tfm;
 125         unsigned long alignmask = crypto_shash_alignmask(parent);
 126         struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
 127         struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
 128         struct crypto_cipher *tfm = tctx->child;
 129         int bs = crypto_shash_blocksize(parent);
 130         u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
 131         u8 *prev = odds + bs;
 132
 133         /* checking the data can fill the block */
 134         if ((ctx->len + len) <= bs) {
 135                 memcpy(odds + ctx->len, p, len);
 136                 ctx->len += len;
 137                 return 0;
 138         }
 139
 140         /* filling odds with new data and encrypting it */
 141         memcpy(odds + ctx->len, p, bs - ctx->len);
 142         len -= bs - ctx->len;
 143         p += bs - ctx->len;
 144
 145         crypto_xor(prev, odds, bs);
 146         crypto_cipher_encrypt_one(tfm, prev, prev);
 147
 148         /* clearing the length */
 149         ctx->len = 0;
 150
 151         /* encrypting the rest of data */
 152         while (len > bs) {
 153                 crypto_xor(prev, p, bs);
 154                 crypto_cipher_encrypt_one(tfm, prev, prev);
 155                 p += bs;
 156                 len -= bs;
 157         }
 158
 159         /* keeping the surplus of blocksize */
 160         if (len) {
 161                 memcpy(odds, p, len);
 162                 ctx->len = len;
 163         }
 164
 165         return 0;
 166 }
 167
 168 static int crypto_cmac_digest_final(struct shash_desc *pdesc, u8 *out)
 169 {
 170         struct crypto_shash *parent = pdesc->tfm;
 171         unsigned long alignmask = crypto_shash_alignmask(parent);
 172         struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
 173         struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
 174         struct crypto_cipher *tfm = tctx->child;
 175         int bs = crypto_shash_blocksize(parent);
 176         u8 *consts = PTR_ALIGN((void *)tctx->ctx, alignmask + 1);
 177         u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1);
 178         u8 *prev = odds + bs;
 179         unsigned int offset = 0;
 180
 181         if (ctx->len != bs) {
 182                 unsigned int rlen;
 183                 u8 *p = odds + ctx->len;
 184
 185                 *p = 0x80;
 186                 p++;
 187
 188                 rlen = bs - ctx->len - 1;
 189                 if (rlen)
 190                         memset(p, 0, rlen);
 191
 192                 offset += bs;
 193         }
 194
 195         crypto_xor(prev, odds, bs);
 196         crypto_xor(prev, consts + offset, bs);
 197
 198         crypto_cipher_encrypt_one(tfm, out, prev);
 199
 200         return 0;
 201 }
 202
 203 static int cmac_init_tfm(struct crypto_tfm *tfm)
 204 {
 205         struct crypto_cipher *cipher;
 206         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 207         struct crypto_spawn *spawn = crypto_instance_ctx(inst);
 208         struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
 209
 210         cipher = crypto_spawn_cipher(spawn);
 211         if (IS_ERR(cipher))
 212                 return PTR_ERR(cipher);
 213
 214         ctx->child = cipher;
 215
 216         return 0;
 217 };
 218
 219 static void cmac_exit_tfm(struct crypto_tfm *tfm)
 220 {
 221         struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
 222         crypto_free_cipher(ctx->child);
 223 }
 224
 225 static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 226 {
 227         struct shash_instance *inst;
 228         struct crypto_alg *alg;
 229         unsigned long alignmask;
 230         int err;
 231
 232         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
 233         if (err)
 234                 return err;
 235
 236         alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
 237                                   CRYPTO_ALG_TYPE_MASK);
 238         if (IS_ERR(alg))
 239                 return PTR_ERR(alg);
 240
 241         switch (alg->cra_blocksize) {
 242         case 16:
 243         case 8:
 244                 break;
 245         default:
 246                 goto out_put_alg;
 247         }
 248
 249         inst = shash_alloc_instance("cmac", alg);
 250         err = PTR_ERR(inst);
 251         if (IS_ERR(inst))
 252                 goto out_put_alg;
 253
 254         err = crypto_init_spawn(shash_instance_ctx(inst), alg,
 255                                 shash_crypto_instance(inst),
 256                                 CRYPTO_ALG_TYPE_MASK);
 257         if (err)
 258                 goto out_free_inst;
 259
 260         alignmask = alg->cra_alignmask | (sizeof(long) - 1);
 261         inst->alg.base.cra_alignmask = alignmask;
 262         inst->alg.base.cra_priority = alg->cra_priority;
 263         inst->alg.base.cra_blocksize = alg->cra_blocksize;
 264
 265         inst->alg.digestsize = alg->cra_blocksize;
 266         inst->alg.descsize =
 267                 ALIGN(sizeof(struct cmac_desc_ctx), crypto_tfm_ctx_alignment())
 268                 + (alignmask & ~(crypto_tfm_ctx_alignment() - 1))
 269                 + alg->cra_blocksize * 2;
 270
 271         inst->alg.base.cra_ctxsize =
 272                 ALIGN(sizeof(struct cmac_tfm_ctx), alignmask + 1)
 273                 + alg->cra_blocksize * 2;
 274
 275         inst->alg.base.cra_init = cmac_init_tfm;
 276         inst->alg.base.cra_exit = cmac_exit_tfm;
 277
 278         inst->alg.init = crypto_cmac_digest_init;
 279         inst->alg.update = crypto_cmac_digest_update;
 280         inst->alg.final = crypto_cmac_digest_final;
 281         inst->alg.setkey = crypto_cmac_digest_setkey;
 282
 283         err = shash_register_instance(tmpl, inst);
 284         if (err) {
 285 out_free_inst:
 286                 shash_free_instance(shash_crypto_instance(inst));
 287         }
 288
 289 out_put_alg:
 290         crypto_mod_put(alg);
 291         return err;
 292 }
 293
 294 static struct crypto_template crypto_cmac_tmpl = {
 295         .name = "cmac",
 296         .create = cmac_create,
 297         .free = shash_free_instance,
 298         .module = THIS_MODULE,
 299 };
 300
 301 static int __init crypto_cmac_module_init(void)
 302 {
 303         return crypto_register_template(&crypto_cmac_tmpl);
 304 }
 305
 306 static void __exit crypto_cmac_module_exit(void)
 307 {
 308         crypto_unregister_template(&crypto_cmac_tmpl);
 309 }
 310
 311 module_init(crypto_cmac_module_init);
 312 module_exit(crypto_cmac_module_exit);
 313
 314 MODULE_LICENSE("GPL");
 315 MODULE_DESCRIPTION("CMAC keyed hash algorithm");
 316 MODULE_ALIAS_CRYPTO("cmac");